Drink whiskey and rum this Noel: sweet! (3,4,7)
I believe the answer is:
wet ones whistle
'drink' is the definition.
(I've seen this before)
'whiskey and rum this noel sweet' is the wordplay.
'whiskey' becomes 'W' (phonetic alphabet: alpha, bravo, charlie etc.).
'and' says to put letters next to each other.
'rum' is an anagram indicator (rum can mean strange or unusual).
'this'+'noel'+'sweet'='thisnoelsweet'
'thisnoelsweet' anagrammed gives 'etoneswhistle'.
'w'+'etoneswhistle'='WET ONES WHISTLE'
(Another definition for wet ones whistle that I've seen is " Have a drink".)